\begin{table}[ht]\centering                  \def\sym#1{\ifmmode^{#1}\else\(^{#1}\)\fi}                   \caption{Composition Effects in Construction Costs\label{tab:composition_L}}                 \setlength{\tabcolsep}{3pt}                         \begin{tabular}{l*{11}{c}}\hline\hline \bigskip\\[6ex]
                &\multicolumn{1}{c}{\LongHead{15ex}{HPMS-Grade}}&\multicolumn{1}{c}{\LongHead{15ex}{Elevation}}&\multicolumn{1}{c}{\LongHead{15ex}{NLCD-Water}}&\multicolumn{1}{c}{\LongHead{15ex}{NLCD-Urban}}&\multicolumn{1}{c}{\LongHead{15ex}{HPMS-Urban}}&\multicolumn{1}{c}{\LongHead{15ex}{Unionization}}&\multicolumn{1}{c}{\LongHead{15ex}{AADT}}&\multicolumn{1}{c}{\LongHead{15ex}{New-miles}}&\multicolumn{1}{c}{\LongHead{15ex}{Structural Number}}&\multicolumn{1}{c}{\LongHead{15ex}{Share rigid}}\\
\hline
\(I^{L}_{st} \) &    0.167         &    0.049         &    0.024         &    0.156\sym{+}  &    0.201\sym{*}  &    0.121         &    0.207\sym{+}  &    0.047\sym{*}  &   -0.120         &    0.009         \\
                &  (0.108)         &  (0.032)         &  (0.046)         &  (0.092)         &  (0.089)         &  (0.074)         &  (0.105)         &  (0.022)         &  (0.167)         &  (0.028)         \\
\(I^{L}_{st} \) $\times$ t&   -0.006         &   -0.003\sym{*}  &   -0.003         &   -0.010\sym{*}  &   -0.013\sym{**} &   -0.009\sym{**} &   -0.012\sym{*}  &   -0.003\sym{**} &    0.011         &   -0.000         \\
                &  (0.004)         &  (0.002)         &  (0.002)         &  (0.004)         &  (0.004)         &  (0.003)         &  (0.005)         &  (0.001)         &  (0.007)         &  (0.002)         \\
t               &    0.041         &   -0.602\sym{*}  &   -0.690\sym{*}  &   -0.525\sym{+}  &   -0.276         &   -0.560         &    0.371         &   -0.729\sym{*}  &   -0.367         &   -0.168         \\
                &  (0.289)         &  (0.284)         &  (0.272)         &  (0.266)         &  (0.337)         &  (0.334)         &  (0.430)         &  (0.313)         &  (0.310)         &  (0.265)         \\
\(x^0\)       &    2.470         &                  &                  &                  &  -44.410         &    0.279         &   -0.138\sym{+}  &   -0.272         &    2.177         &   31.373         \\
                &  (6.976)         &                  &                  &                  & (49.636)         &  (1.326)         &  (0.081)         &  (0.268)         &  (3.403)         & (23.323)         \\
\(x^0\) $\times$ \(I^{L}_{st} \)&   -0.060         &    0.000         &    0.304         &   -0.483         &   -0.289\sym{*}  &   -0.004         &   -0.000\sym{+}  &    0.017         &    0.028         &    0.165         \\
                &  (0.057)         &  (0.000)         &  (0.300)         &  (0.371)         &  (0.138)         &  (0.004)         &  (0.000)         &  (0.017)         &  (0.027)         &  (0.118)         \\
\(x^0\) $\times$ \(I^{L}_{st} \) $\times$ t&   -0.000         &   -0.000         &   -0.010         &    0.029\sym{+}  &    0.019\sym{**} &    0.000\sym{+}  &    0.000\sym{+}  &   -0.000         &   -0.002\sym{+}  &   -0.011\sym{+}  \\
                &  (0.003)         &  (0.000)         &  (0.011)         &  (0.016)         &  (0.007)         &  (0.000)         &  (0.000)         &  (0.001)         &  (0.001)         &  (0.006)         \\
\cline{2-11}State FE        &      Yes         &      Yes         &      Yes         &      Yes         &      Yes         &      Yes         &      Yes         &      Yes         &      Yes         &      Yes         \\
\hline
N               &      799         &    1,171         &    1,171         &    1,171         &    1,171         &    1,171         &    1,171         &    1,006         &      988         &      988         \\
\hline\hline         \multicolumn{11}{l}{ \footnotesize Standard Errors in Parentheses Clustered at the State Level  }\\                 \multicolumn{11}{l}{ \footnotesize  \sym{+} \(p<0.10\), \sym{*} \(p<0.05\), \sym{**} \(p<0.01\), \sym{***} \(p<0.001\).    }                 \end{tabular}   \end{table}
